A mission of a university can be "to educate future leaders," "to educate responsible citizens," "to teach and disseminate certain kind of ideas," "to advance science, the arts, and good literature,""to explore, create, and challenge knowledge," "to change a country," "to change a continent," "to change the world!!!," etc. The mission represents an enormous challenge that requires a lot of good judgment, resources, discipline, and focus [and much more!].
Now, lets imagine a universities [be it public, private, in a developed, or a developing country] can get some resources for free. The consequence is that it is now going to be easier, or not as difficult, to accomplish its mission.
Free online classes offered by Udacity, Coursera [and now Marginal Revolution University!], etc., are free, good quality, resources that universities can take advantage of. Universities worldwide should look at these providers as complements rather than competitors or substitutes [imagine a baker who can get some important ingredients for free! Should he take them?].
The mission of a university is not to teach a sociology class, or a economics class, the mission is much greater than that. Accepting classes offered by online providers just makes it easier [and cheaper!] to accomplish the greater mission.
More specifically, why universities should accept these classes for credit?
1) It is a way to reduce the problem of overcrowding in public universities [think about universities in Cameroon, Nigeria, etc., etc.]. This happens especially in introductory classes, and it is also a common problem in developed countries.
2) This will free some resources for other educational purposes: to teach advanced and interdisciplinary classes, to apply concepts to case studies, to do applied research, etc.
But probably the most important reason is that this will let a university to allocate more resources to accomplish its mission.
In fact, it seems that if universities do not do that [meaning accepting online classes] it is because they are not really mission driven.
Why wasting resources in teaching some knowledge that is already free online, when one can apply it to generate solutions and more knowledge?